Material for "sponge" wall paint
Here is one result you could achieve with noise and voronoi textures:



The concept is fairly simple, first create two base shaders.
 Here it is the two sets of diffuse/ glossy. One for the darker and lighter color of the paint. Then, just mix between them with a noise texture. 

The scale of the noise texture will control how much variation there is between the two layers, and where the variation falls. The color ramp will control the intensity of the transition between the layers. Changing the interpolation to ease or b-spline might be interesting depending on your needs.  

Then use voronoi (or some other texture with high scale) for bump to give the texture of the wall.  

Here is the node setup for the example above:



click to enlarge